Google has released a kit for software developers to create programs for the "G-phone" due out next month in a direct challenge to Apple's hot-selling iPhone.

The Android 1.0 software developers kit lets computer programming wizards customize applications that will work on the open-source platform built into the G1 handsets being brought to market by telecom carrier T-Mobile.

The T-Mobile G1 phones are heralded as the first of a generation of devices built on the Google-led Android operating platform.

Apple recently began letting outside developers customize applications for iPhones and iPod Touch models but vets programs carefully and safeguards details of proprietary software built into its products.

The finished Android developers kit released on Tuesday is a refinement of a "beta" test version that Google has let third-party programmers tinker with for months.

Google already held the first of what is to be an annual "Android Developers Challenge" and gave away five million dollars in prize money for innovative software tailored to the platform.

Google unveiled its long-awaited smart phone on Tuesday. G1 phones will be available in stores in the United States on October 22 and will cost 179 dollars, 20 dollars cheaper than the iPhone 3G.

The G1 will go on sale in Britain in early November and in other European countries served by T-Mobile, a subsidiary of Germany's Deutsche Telekom AG, in early 2009.